That works but the way to look at the 3 skill trees is....
Tactics: The PvP Spec used for DPS types with the use of Combat Tech Armor, very close range but efficient with the use of a knife and fire pulse, knife being up close just like the stockstrike but a lower cooldown. (Used Tactics to 50, was slower in some spots, but it helped it some spots where it had no choice but to hit up close.)
Assault: The Shared Spec between Commando and Vanguard, suitable for both PvP and PvE. Use of Combat Tech Armor as well. A heavier hit with the main DPS Cell being Plasma and Stockstrike. Hitting the very end being the Assault platique use at the range of 10 meters. Also the Incendiary Round at 10 meters
Shield Specialist: The Tank Spec, with use of the Ion Cell you are harder to take down due to Shielding. Used in both PvP and PvE with the use of Supercommando Armor. Ion Cell generates 100% threat so careful if you're trying to avoid a certain Mob. Use of Storm, being able to run up to a foe from 30 meters away and Energy Blast, generating one ammo per shot at 10 Meters (I am currently a Tank and it's my favorite Spec of them, feeling the power to keep everything with me if able in use of taunting.)
Hopefully this helps out with it. Also the Skill Mentor is in the Combat Training Section of Carrick Station, on the lower level on the very left side. Very Easy to find, hopefully it works out for ya. Have out thar!
Yeah, Assault is the only tree that's used in PvP. The other 2 are pretty much PvE exclusive